APPENDIX 627 



is the most satisfactory implement to use. The stem may be cut in two 

 and a- steel rod of good quality welded in to make the auger about 40 

 inches long. 



Ordinarily, samples may well be taken in sets of three : the surface, or 

 average plowed soil (o to 6| inches), the subsurface, or that which can 

 possibly be moved with a subsoil plow (6 to 20 inches), and the subsoil 

 (20 to 40 inches), corresponding to about 2 million, 4 million, and 6 mil- 

 lion pounds, respectively, of ordinary soil. The surface boring is made 

 and the hole enlarged about \ inch in diameter, the soil all being saved. 

 The subsurface boring is then taken and the hole again enlarged, but the 

 extra soil is not saved. Finally the subsoil boring is taken and the soil 

 saved from only one half (one groove) of the auger. This provides about 

 equal quantities of soil from each stratum. 



Preparation of sample. The sample of soil after air-drying is pul- 

 verized to pass through a sieve with round holes i mm. in diameter. Any 

 gravel which does not pulverize as easily as the dried lumps of clay is 

 weighed and its percentage determined, after which it is discarded. 

 For all determinations except reaction and acidity the soil is further 

 pulverized to pass through a zoo-mesh sieve. 



Dry matter. Five grams of soil are placed in a glass weighing tube 

 fitted with glass stopper, heated for eight hours at a temperature of 105 

 to 107 C. in a current of air dried by passing through H 2 SO 4 and CaCl 2 , 

 the stopper replaced, and the tube allowed to cool in a desiccator. On 

 weighing, duplicate samples should check within 5 mg. The results of 

 all analyses are calculated to the dry basis as found by this determination. 



Reaction. The reaction of the soil is determined by the test sug- 

 gested by Veitch (Bulletin 73, page 136, Bureau of Chemistry, United 

 States Department of Agriculture). About 10 g. of soil are placed 

 in a Jena flask with 150 cc. water, thoroughly shaken, and allowed to 

 settle until the water is practically clear. The supernatant liquid is 

 carefully drawn off and boiled down with a few drops of phenolphtha- 

 lein in a Jena beaker (covered with a watch-glass) to about 25 cc. A pink 

 color indicates alkalinity. If no color appears, the soil is either acid or 

 neutral. In case the soil is acid, its acidity, calculated to calcium car- 

 bonate required to neutralize, is determined; and in case it is alkaline, 

 the carbonate carbon present is determined and calculated to calcium 

 carbonate. 



Acidity. Place 100 g. of soil in a 400 cc. wide-mouthed bottle, add 

 250 cc. normal potassium nitrate solution, stopper, and shake continu- 

 ously for three hours in a shaking machine or every five minutes by hand. 

 Let stand over night. Draw off 125 cc. of the clear supernatant liquid, 



